addLogo.R

# Add a logo at the bottom left of a plot (outside plot area).
# obj = raster image
# wight = width in % of figure width
# shift in inch (x, y)
# interpolate Raster (=smooth)
#---
# inspiration: https://stackoverflow.com/a/56018973/16599100
addLogo <- function(obj, width = 0.25, shift = c(0,0), interpolate = TRUE){
  xsign <- ifelse(diff(par()$usr[1:2]) > 0, 1, -1)
  ysign <- ifelse(diff(par()$usr[3:4]) > 0, 1, -1)
  W <- abs(diff(par()$usr[1:2]))
  H <- abs(diff(par()$usr[3:4]))
  PIN <- par()$pin
  x0 <- par()$usr[1] + xsign * (shift[1] - par()$mai[2])/PIN[1]*W
  y0 <- par()$usr[3] + ysign * (shift[2] - par()$mai[1])/PIN[2]*H 
  DIM <- dim(obj) # number of x-y pixels for the image
  ARp <- DIM[1]/DIM[2] # pixel aspect ratio (y/x)
  wobj <- width * W
  hobj <- wobj * ARp * H/W * PIN[1]/PIN[2]
  par(xpd = NA)
  rasterImage(image = obj, 
              xleft = x0, xright = x0 + xsign * wobj,
              ybottom = y0, ytop = y0 + ysign * hobj, 
              interpolate = interpolate)
  par(xpd = FALSE)
  
}